Cathode ray tube focusing device



March 31, 1959 w. F. sTEERs 2,880,343

CATHQDE RAY TUBE FocusING DEVICE Filed Dec. 12, 1955 IN VEN TOR. ,WAM/,sw 575595 United Staes Patent C CATHODE RAY TUBE FOCUSING DEVICE William F. Steers, Short Hills, NJ., assignor to Glaser- Steers Corporation, a corporation of New Jersey Application December 12, 1955, Serial No. 552,487

4 Claims. (Cl. 313-84) The present invention relates to cathode ray tube focusing devices and is directed particularly to the cathode ray tube focusing devices of the permanent magnet type with a member for centering the electron beam.

An object of this invention is to provide a cathode ray tube focusing device that accurately and easily focuses and centers the electron beam of the cathode ray tube.

Another object of the invention is to provide a cathode ray tube focusing device that comprises a minimum number of particulars for optimum performance and is easily and inexpensively assembled.

Another further object of the invention is to provide a cathode ray tube focusing device that has a centering member that is easily manipulated and locked in position.

A still further object of the invention is to provide a cathode ray tube focusing device that easily focuses the electron beam and retains the adjustment.

Other and further objects and advantages will be apparent from the following description taken in connection with the drawings in which:

Fig. l is a front view of the cathode ray tube focusing device;

Fig. 2 is a rear view of the focusing device;

Fig. 3 is a sectional view of Fig. 2 taken along line 3-3 of Fig. 2; and

Fig. 4 is a fragmentary sectional view of the adjusting mechanism.

Referring to the drawings, there is shown a focusing unit having a mounting plate secured to supports 11 and 12 attached to a television chassis (not shown). They bolts 13 and 14 extend through elongated slots 1S and 16 in the mounting plate 10 and are securely fastened by wing nuts 17 and 18. A permanent ring-shaped magnet 20 is pivotally secured to the mounting plate 10 by means of a ring-shaped supporting member 21 having ears 22 and 23 extending laterally therefrom. Bolts 24 and 25 extend through the mounting plate 10 and are threaded in the supporting member 21 to firmly hold the magnet against the plate. Notches are provided in magnet 20 to recess the bolts and position the ears on the magnet to press against the magnet. "the mounting plate 10 and the ring-shaped magnet 20 have axially aligned circular openings 28 and 29 respectively. The opening 28 in the plate is substantially larger than the opening 29 in the permanent magnet to permit the mounting of a centering plate 30 on the magnet. The centering plate has a flat portion 31 bearing against the at surface 32 of the magnet. A ange 33 extends normally thereto in a direction normal to the magnet.

The centering plate 30 is held against the surface 32 of the permanent magnet by a circular yoke 35 and straps 36 and 37. The straps 36 and 37 are secured to the mounting plate 10 by means of a rivet 3S rigidly secured in the upper portion of the mounting plate 10 and passing through a slot 39 in the strap 36'. The rivet has a head 38a holding a spring washer 40 against a at metal washer 41 to resiliently press the strap 36 against the 2,880,343 Patented Mar. 31, 1959 ICC mounting plate 10. The strap 37 extending from the opposite side of the yoke 30 is secured to the mounting plate by means of the pin 42 extending through a lateral slot 43 in the plate 10 and a longitudinal slot 44 in the strap 37. The pin has heads or turned ends to hold the plate and strap together. A grip 45 extends normal to the strap 37 for adjusting the yoke and centering plate 30. The pin 42 pivotally holds the locking lever 46 on the strap 37. The locking lever 46 has a wedge 47 engaging the strap 37 to press the strap against the mounting plate 10 to lock the yoke 35 and the centering plate 30 in position.

it is thus seen that the centering plate is held by the magnet 20 and the yoke 35 and is adjustably positioned by the yoke engaging the flange 33 and sliding the centering plate on the surface of the permanent magnet.

The intensity of the eld of the magnet within the television tube 50 indicated by the dotted lines is controlled by the axially movable shunt 51. The shunt 51 is tubular in shape and fits around the tube 50 indicated by dot and dash line. The exterior surface has threads 52 which engage threads in complementary supporting ring 21 so that as the shunt 51 is rotated about the longitudinal axis, the gap A between the forward end of the shunt 51 and the centering plate 30 is varied.

At the other end of the shunt 51 a ring gear of nonmagnetic material is press fitted thereon and has peripheral teeth 54 extending around the entire circumference of the gear. A stud gear 55 is rotatably mounted on the supporting member 21 and has longitudinally extending teeth 56 thereon engaging the teeth 54 to rotate the shunt 51. The teeth 54 slide longitudinally on the teeth 56 as the shunt 51 moves. The stud gear has a knurled knob 57 for turning the gear 55 and a collar 58 between the gear and the handle. The ring gear engages the collar to limit the extension of the shunt 51 out of the permanent magnet 20. The stud gear 56 is pivotally secured to the mounting member 21 by a pin or projection 60, preferably formed as a single piece with the gear 56. The pin 60 extends through the supporting member 21. The end of the pin 60 is peened over onto a washer 62 to fasten the gear to the member 21. Thus the shunt 51 is telescopically mounted to move longitudinally within the permanent magnet 20 to vary the amount of ux within the opening 29.

The magnet 20 is a permanent magnet and is preferably of barium ferrite. The supporting member 21 and the centering member 30 are made of magnetic material. The shunt 51 is also made of magnetic material to provide a ux path between the member 21, centering member 30, and the ends of the magnet 2G. The shunt is threaded in the member 21 to provide a direct contact with the magnet and is adjustably positioned in relation to the centering member 30 to form a generally cylindrical variable air space A, through which the magnetic lines of force pass. The length of the space is varied by the longitudinal movement of the shunt 51 and the general concentricity of the space may be changed by the adjustment of the position of the centering member 30 on the surface 32 of the magnet.

The lines of force extend from the surface 32 of the permanent magnet 20 to the surface 32a and pass into the neck of the cathode ray tube 50. The lines of force pass through and are concentrated in the centering plate 30, the shunt 51, and the mounting 21 by adjusting the distance A between the shunt 51 and the centering plate 30. The amount of ux extending into the cathode ray tube is varied. When the shunt 52 is positioned within the permanent magnet, the distance A is at a minimum. When the shunt is threaded to engage the collar 58, the distance A is at a maximum and substantially all other flux extends into the neck of the tube.

Thus by two adjustments that may be easily made and retained, the flux of the magnet within the cathode ray tube may be shifted and increased and decreased in intensity.

Another advantage is that the device is easily assembled. The focusing device is assembled by threading the shunt 51 in the member 21, fitting the stud gear to engage the ring gear 53 and securing the gear to the plate 21 by forcing the rivet 60 into the stud gear and turning the head to secure the stud gear to the member 21. This assembly may then be mounted on the mounting plate and securing the permanent magnet thereto by the bolts 24 and 25.

I claim:

1. A magnetic focusing and centering device for a cathode ray tube having a neck and a screen with an electron beam passing through the neck and impinging on the screen and comprising a ring shaped permanent magnet having a bore extending longitudinally therethrough and laterally extending end surfaces, a mounting plate at one end of said magnet, a supporting member at the other end of said magnet, fastening means securely holding said mounting plate and said supporting member to clamp said magnet in place therebetween, said supporting member having an inner circular edge with threads, a magnetic shunt fitting within the bore of the permanent magnet and having an outer threaded surface complementary to the threads on said inner circular edge and threaded therein through said shunt longitudinally within said magnet to vary the flux within the neck of the cathode ray tube, said shunt having a ring gear on the end thereof, a seco-nd gear rotatably mounted on said supporting member engaging said first gear to rotate said first gear while moving said shunt longitudinally within said permanent magnet to focus an electron beam, an electron beam centering the plate having a at laterally extending portion bearing on the end surface of said permanent magnet and having an opening with a small diameter in the bore of the permanent magnet to extend inwardly of said bore for carrying the ux of the magnet into the neck of the cathode ray tube, said centering plate having a ange extending laterally therethrough, a separate non-metallic yoke fitting on said centering plate in engagement with said ange to adjust the position of said centering plate in relation to said magnet to vary the focused magnetic field within the bore of said magnet for positioning an electron beam passing therethrough.

2. A magnetic focusing and centering device for a cathode ray tube comprising a ring shaped permanent member having a bore therethrough and having lateral end surfaces, a mounting plate at one end of said magnet, a supporting member at the other end of said magnet, fastening means connected to said plate and said member to securely clamp said magnet in place on said mounting plate, an electron beam centering plate having a tlat laterally extending portion bearing directly on said permanent magnet and having a flange normal thereto, a separate non-magnetic yoke in engagement with said flange, said yoke having a strap extending adjacent said mounting plate to support said centering plate in relation to said magnet, said strap and said mounting plate each having slots extending crosswise to one another and securing means extending through the slots to fasten said strap and yoke to said mounting plate and to permit a universal movement of one yoke in a plane parallel to the end of the magnet, a locking member with a cam, a pin extending through said slots and pivotally mounting said locking member on said strap and mounting plate with a cam forcing said strap against said mounting plate to lock the strap and yoke in position.

3. A magnetic focusing and centering device for a cathode ray tube producing an electron beam passing through the neck of the tube and impinging on the screen of the tube and comprising a generally cylindrical permanent magnet having a longitudinally extending opening for fitting the magnet around the neck of a cathode ray tube, supporting means having a mounting plate at one end of said permanent magnet with a second opening larger than the opening of said permanent magnet to provide a radial surface of said permanent magnet within said second opening and having a supporting member at the other end of said magnet, fastening means engaging said supporting member for securely clamping said permanent magnet to said mounting plate, an electron beam centering plate for adjusting the position of the electron beam on the screen of the cathode ray tube, said centering plate having a flat portion bearing directly on the surface of said permanent magnet and having an opening smaller than said permanent magnet to transmit the ux from said magnet into said longitudinally extending opening, said centering plate having a flange portion extending laterally to said flat portion on the side opposite from said permanent magnet, a separate non-magnetic yoke having means for mounting said yoke on said mounting plate for movement of said yoke in a plane transverse to said magnet, said yoke bearing generally axially against said at portion and engaging said flange for holding and positioning said centering plate on said permanent magnet to vary the position of the field within the first opening, said supporting member having an inner circular edge forming an opening for passing the neck of a cathode ray tube and telescopically supporting a cylindrically shaped magnetic shunt within the opening of said permanent magnet, said edge and shunt having threads to move said shunt longitudinally within said magnet to vary the ux, said shunt having a ring gear on the outer end thereof, a second gear rotatably mounted on said supporting member and engaging said first gear to longitudinally move said shunt to vary the centered flux extending within the longitudinally extending opening between said centering plate and said shunt.

4. A magnetic focusing and centering device comprising front and rear mounting plates, a generally cylindrically shaped permanent magnet having end surfaces and a generally cylindrical bore extending axially therethrough, fastening means extending through said plates to securely fasten the permanent magnet to the front mounting plate, said front mounting plate having an opening larger than the diameter of the cylindrical bore to form a recess with the front end surface of the permanent magnet, a ring shaped centering plate of mag'- netic material having a rim with a center opening less than the diameter of the bore and a ange extending axially from the inner edge to project generally normal to the magnet, a separate mounting magnetic positioning member having means for adjustably fastening said posi-` tioning member to move in a plane normal to said permanent magnet and having a yoke portion engaging the flange and rim of the centering plate for supporting and positioning said centering plate for adjusting the magnetic ux within said bore.

References Cited in the file of this patent UNITED STATES PATENTS 2,416,687 Fry Mar. 4, 1947 2,418,487 Sproul Apr. 8, 1947 2,580,606 Schiel et al. Jau. 1, 1952 2,581,657 Heppner Jan. 8, 1952 2,591,820 Jackson Apr. 8, 1952 2,592,185 Quam Apr. 8, 1952 2,664,514 Reiches et al. Dec. 29, 1953 

